-x + 3/7 = 2x - 25/7

3x = 4

x = 4/3

Add x (1x) to both sides:

3/7 = 3x - 25/7

Add 25/7 to both sides

28/7 = 3x

Reduce

4 = 3x

Divide both sides by 3

4/3 = x